cgroups: fix cgroup mounting

Cc: stable-4.0
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index 1df135d946a09a8d18a70055de4bc7d2eb51d14e..138d01ee2eb194692df56199bf539ce1ace489dc 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -1871,13 +1871,21 @@ __cgfsng_ops static bool cgfsng_mount(struct cgroup_ops *ops,
                return cg_mount_cgroup_full(type, ops->unified, cgroup_root) == 0;
        }
 
-       /* mount tmpfs */
-       ret = safe_mount_beneath(root, NULL, DEFAULT_CGROUP_MOUNTPOINT, "tmpfs",
+       /*
+        * Mount a tmpfs over DEFAULT_CGROUP_MOUNTPOINT. Note that we're
+        * relying on RESOLVE_BENEATH so we need to skip the leading "/" in the
+        * DEFAULT_CGROUP_MOUNTPOINT define.
+        */
+       ret = safe_mount_beneath(root, NULL,
+                                DEFAULT_CGROUP_MOUNTPOINT_RELATIVE,
+                                "tmpfs",
                                 MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME,
                                 "size=10240k,mode=755");
        if (ret < 0) {
                if (errno != ENOSYS)
-                       return false;
+                       return log_error_errno(false, errno,
+                                              "Failed to mount tmpfs on %s",
+                                              DEFAULT_CGROUP_MOUNTPOINT);
 
                ret = safe_mount(NULL, cgroup_root, "tmpfs",
                                 MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME,

diff --git a/src/lxc/cgroups/cgroup.h b/src/lxc/cgroups/cgroup.h
index 7dec05a5c2506065b0626674200deb2bd4214c91..b8a4d0f5bfa5847cdb23471b2eec4647b0d193f8 100644 (file)
--- a/src/lxc/cgroups/cgroup.h
+++ b/src/lxc/cgroups/cgroup.h
@@ -11,6 +11,7 @@
 #include "macro.h"
 #include "memory_utils.h"
 
+#define DEFAULT_CGROUP_MOUNTPOINT_RELATIVE "sys/fs/cgroup"
 #define DEFAULT_CGROUP_MOUNTPOINT "/sys/fs/cgroup"
 #define DEFAULT_PAYLOAD_CGROUP_PREFIX "lxc.payload."
 #define DEFAULT_MONITOR_CGROUP_PREFIX "lxc.monitor."

diff --git a/src/lxc/utils.c b/src/lxc/utils.c
index c4815d14c7dfab2a504fb7b0cebfea88aa65965f..1e0b38e121b63f2da4ef9cf965124cb294b6cc05 100644 (file)
--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -1103,7 +1103,7 @@ int __safe_mount_beneath_at(int beneath_fd, const char *src, const char *dst, co
 
        target_fd = openat2(beneath_fd, dst, &how, sizeof(how));
        if (target_fd < 0)
-               return -errno;
+               return log_error_errno(-errno, errno, "Failed to open %d(%s)", beneath_fd, dst);
        ret = snprintf(tgt_buf, sizeof(tgt_buf), "/proc/self/fd/%d", target_fd);
        if (ret < 0 || ret >= sizeof(tgt_buf))
                return -EIO;